1. Field of the Invention
The present invention relates to an optical disk on which information (e.g., digital video information) can be stored at a high density.
2. Description of the Related Art
In recent years, the recording density of optical disk media goes on increasing. On an optical disk medium, a track groove has normally been formed in advance and a recording film has been formed so as to cover the track groove. Data or information is written by the user on the recording film along the track groove, i.e., either on the track groove or on an area (land) interposed between adjacent parts of the track groove.
The track groove is formed so as to wobble just like a sine wave and a clock signal is generated in accordance with a wobble period. Synchronously with this clock signal, user data is written on, or read out from, the recording film.
To write data at a predetermined position on an optical disk, address information (positional information), indicating physical locations on the optical disk, needs to be allocated to, and recorded at, respective sites on the optical disk while the disk is being manufactured. Normally, an address is allocated to a series of areas that are arranged along a track groove and have a predetermined length. There are various methods for recording such address information on an optical disk. Hereinafter, a conventional method for recording an address on an optical disk will be described.
Japanese Laid-Open Publication No. 6-309672 discloses a disk storage medium on which a wobbling track groove is discontinued locally so that an address-dedicated area is provided for the discontinued part. Pre-pits, representing address information recorded, are formed on the address-dedicated area on the track groove. This optical disk has a structure in which the address-dedicated area and a data-dedicated area (for writing information thereon) coexist on the same track groove.
Japanese Laid-Open Publication No. 5-189934 discloses an optical disk on which address information is recorded by changing the wobble frequency of a track groove. In an optical disk like this, an area on which the address information is recorded and an area on which data will be written are not separated from each other along the track.
Japanese Laid-Open Publication No. 9-326138 discloses an optical disk on which pre-pits are formed between adjacent parts of a track groove. These pre-pits represent the address information recorded.
These various types of optical disks have the following problems to be solved for the purpose of further increasing the recording density.
First, as for the optical disk on which address information is recorded as pre-bits within the address-dedicated area on the track, a so-called xe2x80x9coverheadxe2x80x9d occurs to secure the address-dedicated area and the data area should be reduced disadvantageously. As a result, the storage capacity available for the user has to be reduced.
Next, as for the optical disk for recording an address thereon by modulating the wobble frequency of the track, a write clock signal cannot be generated precisely enough. Originally, the wobble of the track groove is created mainly to generate a clock signal for establishing synchronization required for read and write operations. Where the wobble frequency is single, a clock signal can be generated highly precisely by getting a read signal, having amplitude changing with the wobble, synchronized and multiplied by a PLL, for example. However, if the wobble frequency is not single but has multiple frequency components, then the frequency band that the PLL can follow up should be lowered (as compared to the situation where the wobble has a single frequency) to avoid pseudo locking of the PLL. In that case, the PLL cannot sufficiently follow up the jitter of a disk motor or a jitter resulting from the eccentricity of a disk. Thus, some jitter might remain in the resultant recording signal.
On the other hand, where the recording film formed on the optical disk is a phase-change film, for example, such a recording film may result in a decreased SNR as the data stored on the film is altered repeatedly. If the wobble frequency is single, the noise components are removable using a band-pass filter having a narrow band. However, if the wobble frequency has been modulated, the filter should have its bandwidth broadened. As a result, the noise components are much more likely contained and the jitter might be further worsened. It is expected that the recording density will be further increased from now on. However, the higher the recording density, the narrower the allowable jitter margin will get. Accordingly, it will be more and more necessary to minimize the increase in jitter by avoiding the modulation of the wobble frequency.
In the structure in which the pre-pits representing the address information recorded are formed between adjacent parts of the groove, it is difficult to form long enough pre-pits in sufficiently large numbers. Accordingly, as the recording density is increased, detection errors might increase its number. This is because if large pre-pits are formed between adjacent parts of the groove, then those pits will affect adjacent parts of the track.
In order to solve the problems described above, a main object of the present invention is to provide an optical disk medium that contributes to minimizing the overhead and generating a clock signal precisely enough in accordance with the wobble of the track groove.
Another object of this invention is to provide a method and apparatus for reading an address that has been recorded on the optical disk medium.
An optical disk medium according to the present invention includes a track groove. On the optical disk medium, information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. Subdivided information allocated to each said unit section is represented by a shape given to the unit section.
In a preferred embodiment, the side faces of the track groove are displaced either toward inner or outer periphery of the disk with respect to a centerline of the track groove.
In another preferred embodiment, the information is recorded on a block-by-block basis. Each said block has a predetermined length and includes a number N of unit sections that are arranged along the track groove.
In another preferred embodiment, part of the side faces that is shared by at least two of the unit sections has a constant displacement period within at least one of the blocks.
In another preferred embodiment, one-bit subdivided information is allocated to each said unit section, and a group of subdivided information representing N bits is recorded on the N unit sections that are included in each said block.
In another preferred embodiment, each said N-bit subdivided information group includes address information of its associated block to which the unit sections, where the subdivided information group is recorded, belong.
In another preferred embodiment, each said N-bit subdivided information group includes an error correction code and/or an error detection code.
In another preferred embodiment, the error correction code or the error detection code has its ability to correct an error of the address information weighted in such a manner that low-order bits of the error correction or detection code have a relatively large weight.
In another preferred embodiment, each said unit section has a first side displacement pattern that has been so defined as to make a signal waveform rise relatively steeply and fall relatively gently or a second side displacement pattern that has been so defined as to make a signal waveform rise relatively gently and fall relatively steeply.
An inventive address reading method is a method for reading subdivided information from an optical disk medium, which includes a track groove and on which information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. The subdivided information allocated to each said unit section is represented by a shape given to the unit section. The side faces of each said unit section are displaced according to a pattern to be selected from first and second wobble patterns that have the same fundamental frequency but mutually different shapes. In this method, the subdivided information allocated to each said unit section is identified by comparing a number of times the first wobble pattern has been detected from the unit section with a number of times the second wobble pattern has been detected from the unit section.
In a preferred embodiment, if a difference between the number of times the first wobble pattern has been detected from each said unit section and the number of times the second wobble pattern has been detected from the unit section falls within a predetermined range, then the subdivided information allocated to the unit section is error-corrected.
In another preferred embodiment, a type of a given wobble pattern is identified by a gradient of a leading or trailing edge of a signal corresponding to the wobble pattern.
In another preferred embodiment, the type of the given wobble pattern is identified by comparing an absolute gradient value of the leading edge of the signal to an absolute gradient value of the trailing edge thereof.
An optical disk reproducing apparatus according to the present invention is an apparatus for reading subdivided information from an optical disk medium, which includes a track groove and on which information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. The subdivided information allocated to each said unit section is represented by a shape given to the unit section. The side faces of each said unit section are displaced according to a pattern to be selected from first and second wobble patterns that have the same fundamental frequency but mutually different shapes. The apparatus includes: an optical head, which irradiates the optical disk medium with light and generates an electric signal responsive to part of the light that been reflected from the optical disk medium; read signal processing means for generating a wobble signal, which has amplitude changing with the wobble pattern, from the electric signal; rise value acquiring means for sampling and holding an absolute gradient value of the wobble signal when the signal rises; fall value acquiring means for sampling and holding an absolute gradient value of the wobble signal when the signal falls; and subdivided information detecting means for determining the subdivided information by majority by comparing the values held by the rise and fall value acquiring means with each other.
Another optical disk reproducing apparatus according to the present invention is an apparatus for reading subdivided information from an optical disk medium, which includes a track groove and on which information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. The subdivided information allocated to each said unit section is represented by a shape given to the unit section. The side faces of each said unit section are displaced according to a pattern to be selected from first and second wobble patterns that have the same fundamental frequency but mutually different shapes. The apparatus includes: an optical head, which irradiates the optical disk medium with light and generates an electric signal responsive to part of the light that been reflected from the optical disk medium; read signal processing means for generating a wobble signal, which has amplitude changing with the wobble pattern, from the electric signal; timing generating means for generating a timing signal that defines a timing at which the wobble signal rises, a timing at which the wobble signal falls and a timing at which the subdivided information is sectioned; first shape counting means for detecting the first wobble pattern responsive to the timing signal and counting the number of times the first wobble pattern has been detected; second shape counting means for detecting the second wobble pattern responsive to the timing signal and counting the number of times the second wobble pattern has been detected; and subdivided information detecting means for determining the subdivided information by majority by comparing counts of the first and second shape counting means with each other.
Another optical disk reproducing apparatus according to the present invention is an apparatus for reading subdivided information from an optical disk medium, which includes a track groove and on which information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a single fundamental period. The subdivided information allocated to each said unit section is represented by a shape given to the unit section. The side faces of each said unit section are displaced according to a pattern to be selected from first and second wobble patterns that have the same fundamental frequency but mutually different shapes. The apparatus includes: an optical head, which irradiates the optical disk medium with light and generates an electric signal responsive to part of the light that been reflected from the optical disk medium; read signal processing means for generating a wobble signal, which has amplitude changing with the wobble pattern, from the electric signal; timing generating means for generating a timing signal that defines a timing at which the wobble signal rises, a timing at which the wobble signal falls and a timing at which the subdivided information is sectioned; first shape counting means for detecting the first wobble pattern responsive to the timing signal and counting the number of times the first wobble pattern has been detected; second shape counting means for detecting the second wobble pattern responsive to the timing signal and counting the number of times the second wobble pattern has been detected; subdivided information detecting means for determining the subdivided information by majority by comparing counts of the first and second shape counting means with each other; erasure detecting means for outputting an erasure flag if a difference between the counts of the first and second shape counting means falls within a predetermined range; and error correcting means for conducting error correction in accordance with outputs of the subdivided information detecting means and the erasure detecting means and generating address information.
Another optical disk medium according to the present invention includes a track groove. On the optical disk medium, positional information indicating a physical location on the track groove is represented by a wobble shape of the track groove. The optical disk medium includes a plurality of positional information units that are arranged on the track groove. Each said positional information unit includes: a positional information section that represents the positional information by a combination of wobble patterns selected from multiple types of wobble patterns; and a sync mark section having a wobble pattern in a shape distinguishable from the wobble patterns of the positional information section.
In a preferred embodiment, the optical disk medium includes a precision positioning mark section ahead of each said positional information section.
In another preferred embodiment, the precision positioning mark section is disposed at the beginning of each said positional information unit.
In another preferred embodiment, the precision positioning mark section has a wobble pattern in a shape distinguishable from the wobble pattern of the sync mark section.
In another preferred embodiment, the precision positioning mark section has a wobble pattern in a shape distinguishable from the wobble patterns of the positional information section.
In another preferred embodiment, each said wobble pattern in the positional information section includes: a first part having a smooth sine wave shape; and a second part in which a disk-inner-periphery-oriented displacement and/or a disk-outer-periphery-oriented displacement have/has a shape steeper than the part having the sine wave shape.
In another preferred embodiment, the wobble pattern in the sync mark section includes the first part and/or the second part.
In another preferred embodiment, the precision positioning mark section includes an identification mark for use in precision positioning.
In another preferred embodiment, the identification mark is a mirror mark that has been formed by discontinuing a part of the track groove.
In another preferred embodiment, the mirror mark is disposed at the second through fourth period parts of the wobble pattern in the precision positioning mark section.
In another preferred embodiment, the wobble pattern in the precision positioning mark section has a sine wave shape.
In another preferred embodiment, in each said positional information unit, the precision positioning mark section, the positional information section and the sync mark section are arranged in this order.
In another preferred embodiment, a recording block, which is a smallest read/write unit, includes a number L of the positional information units (where L is a natural number).
In another preferred embodiment, the recording block corresponds to a data unit that constitutes an error correction code.
In another preferred embodiment, writing on the recording block is either started or ended behind a start point of the precision positioning mark section by a predetermined length.
In another preferred embodiment, writing on the recording block is either started or ended behind the mirror mark by a predetermined length.
In another preferred embodiment, the mirror mark has a length of 1 xcexcm to 10 xcexcm as measured along the track groove.
In another preferred embodiment, a single subdivided information unit is represented by a wobble for M periods (where M is a natural number equal to or greater than 2), and one bit of the positional information is allocated to each said subdivided information unit.
In another preferred embodiment, the sync mark section is a combination of first and second wobble patterns, the number of which is N (which is a natural number). In each said first wobble pattern, a wobble, having rectangular parts in which disk-inner-periphery-oriented and disk-outer-periphery-oriented displacements are both steep, is repeated for a number M of periods. In each said second wobble pattern, a smooth sine wave wobble is repeated for the M periods.
In another preferred embodiment, the sync mark section is made up of the first wobble patterns only.
In another preferred embodiment, the first and second wobble patterns are arranged alternately in the sync mark section.
In another preferred embodiment, the sync mark section is a combination including both a transition point from the first wobble pattern into the second wobble pattern and a transition point from the second wobble pattern into the first wobble pattern.
In another preferred embodiment, supposing the positional information is represented by A bits; the sync mark section has a length corresponding to B wobble periods; the precision positioning mark section, including the mirror mark, has a length corresponding to C wobble periods; one wobble period has a length corresponding to W channel bits of recording data; the number of channel bits of a recording block, which is a smallest read/write unit, is D; and the number of the positional information units allocated to each said recording block is E, where A, B, C, E, M and W are all natural numbers, an equation D=(Axc3x97M+B+C)xc3x97Wxc3x97E is satisfied.
In another preferred embodiment, B is a multiple of M.
In another preferred embodiment, A=48, M=32, B=128, C=8, W=186 and E=4.
In another preferred embodiment, A=48, M=36, B=144, C=9, W=155 and E=4.
In another preferred embodiment, A=48, M=24, B=96, C=6, W=186 and E=4.
In another preferred embodiment, A=48, M=36, B=144, C=9, W=124 and E=4.
The optical disk medium may use a modulation code for converting 8 bits into F channel bits. Supposing the precision positioning mark section, including the mirror mark, has a length corresponding to C wobble periods; one wobble period has a length corresponding to W channel bits of recording data; the precision positioning mark section has a length corresponding to P frames of the recording data; one subdivided information unit has a length corresponding to Q frames of the recording data; and one frame of the recording data has a number R of bytes, where C, F, W and R are natural numbers and P and Q are rational numbers, equations Pxc3x97Rxc3x97F=Cxc3x97W and Qxc3x97Rxc3x97F=Mxc3x97W are both satisfied.
In a preferred embodiment, F=16, M=32, C=8, W=186, P=1, Q=4 and R=93.
In another preferred embodiment, F=15, M=36, C=9, W=155, P=1, Q=4 and R=93.
In another preferred embodiment, F=12, M=24, C=6, W=186, P=1, Q=4 and R=93.
In another preferred embodiment, F=12, M=36, C=9, W=124, P=1, Q=4 and R=93.
An inventive positional information reading method is a method for reading out positional information from the optical disk medium of the present invention. The method includes the steps of: detecting the sync mark section that has been formed on the optical disk medium; detecting the precision positioning mark; establishing a bit synchronization for the positional information using the sync mark detected and/or the precision positioning mark detected; and reading out the positional information in accordance with the bit synchronization established in the step of establishing the bit synchronization for the positional information.
An inventive data writing method is a method for writing data on the optical disk medium of the present invention. The method includes the steps of: detecting the sync mark section that has been formed on the optical disk medium; detecting the precision positioning mark based on the sync mark section detected; performing positioning using the precision positioning mark detected; and starting to write the data based on a positioning result obtained in the positioning step.
An optical disk reproducing apparatus according to the present invention is an apparatus for reading out positional information from the optical disk medium of the present invention. The drive includes: means for detecting the sync mark section that has been formed on the optical disk medium; means for generating a first detection window with a predetermined time width after a predetermined time has passed since a timing at which the sync mark was detected by the sync mark detecting means; means for detecting the identification mark, which has been formed on the optical disk medium, by using the first detection window; means for establishing a bit synchronization for the positional information, which is recorded on the optical disk medium, by using the timing at which the sync mark has been detected and/or a timing at which the identification mark has been detected; and means for reading out the positional information at a timing at which the bit synchronization has been established by the means for establishing the bit synchronization for the positional information.
An optical disk recording apparatus according to the present invention is an apparatus for writing data on the optical disk medium of the present invention. The drive includes: means for detecting the sync mark section that has been formed on the optical disk medium; means for generating a first detection window with a predetermined time width after a predetermined time has passed since a timing at which the sync mark was detected by the sync mark detecting means; means for detecting the identification mark, which has been formed on the optical disk medium, by using the first detection window; and data writing means for setting a data writing start point or end point by reference to a timing at which the identification mark has been detected.
Another optical disk medium according to the present invention includes a track groove. On the optical disk medium, information is recorded along the track groove. The track groove includes a plurality of unit sections that are arranged along the track groove and that have side faces displaced periodically along the track groove. The side faces of the unit sections are displaced in a common period. Subdivided information allocated to each said unit section is represented by a shape given to the unit section. On this optical disk medium, control information is represented by a combination of the subdivided information.
In a preferred embodiment, the control information is recorded on a non-user area.
Another optical disk medium according to the present invention includes a track groove. On the optical disk medium, information is recorded along the track groove. Management information of the optical disk medium is represented by wobbling of the track groove.
In a preferred embodiment, the control information is represented by a combination of mutually different wobble waveforms that oscillate at the same frequency.
In another preferred embodiment, the control information is represented by a combination of wobble shapes including: a smooth sine wave part; and a rectangular part in which a disk-inner-periphery-oriented displacement and/or a disk-outer-periphery-oriented displacement are/is steep.
Another optical disk medium according to the present invention includes a track groove on a recording surface thereof. On the optical disk medium, information is recorded along the track groove on the basis of a block unit having a predetermined length. An identification mark, indicating the beginning of each said block unit, has been formed on the track groove. A signal having a particular pattern is overwritten on the identification mark.
In a preferred embodiment, the identification mark is located substantially at the center of an area on which the signal is written.
In another preferred embodiment, the identification mark is located closer to a previous block with respect to the center of an area on which the signal is written.
In another preferred embodiment, the identification mark includes a flat portion that has been formed by discontinuing the track groove for a short interval.
In another preferred embodiment, the identification mark includes a plurality of sub-marks.
In another preferred embodiment, the track groove wobbles periodically. The identification mark is formed by connecting together a plurality of areas of the track groove that have mutually different wobble phases.
In another preferred embodiment, the track groove is provided with a periodic wobble. The identification mark has a frequency different from a frequency of the wobble.
In another preferred embodiment, each said block unit having the predetermined length includes a plurality of sub-blocks that are arranged along the groove. A sub-block identification mark is provided within each said sub-block.
In another preferred embodiment, the track groove is provided with a periodic wobble. A wobble having a frequency different from that of the other parts is allocated to each said sub-block identification mark.
In another preferred embodiment, each said sub-block identification mark is located at the beginning of its associated sub-block.
In another preferred embodiment, the identification mark for one of the sub-blocks included in each said block unit having the predetermined length represents subdivided information indicating an address of the block unit.
In another preferred embodiment, the wobble of the track groove has a shape corresponding to the information indicating the address of each said block unit.
An inventive signal writing method is a method for writing a signal on an optical disk medium including a track groove on a recording surface thereof. On the optical disk medium, information is recorded along the track groove on the basis of a block unit having a predetermined length, and an identification mark, indicating the beginning of each said block unit, has been formed on the track groove. Writing is started before the identification mark, located at the beginning of at least one block unit on which the signal should be written, is reached. The writing is ended after the identification mark, located at the end of the at least one block unit on which the signal should be written, has been passed.
Another inventive signal writing method is a method for writing a signal on an optical disk medium including a track groove on a recording surface thereof. On the optical disk medium, information is recorded along the track groove on the basis of a block unit having a predetermined length. An identification mark, indicating the beginning of each said block unit and including a plurality of sub-marks, has been formed on the track groove. Writing is started after the first one of the sub-marks, included in the identification mark located at the beginning of at least one block unit on which the signal should be written, has been detected. The writing is ended after the last one of the sub-marks, included in the identification mark located at the end of the at least one block unit on which the signal should be written, has been detected.
In a preferred embodiment, a signal having a particular pattern is overwritten on each said identification mark.
In another preferred embodiment, the signal having the particular pattern is a VFO signal.